Pressure relief valve assembly



june 30, 1970 w ELROD PRESSURE RELIEF VALVE ASSEMBLY Filed July l0, 1968 #mtl United States Patent O U.S. Cl. 137-557 6 Claims ABSTRACT OF THE DISCLOSURE A pressure relief valve assembly for a vessel containing a vaporizable uid has a pair of spring-loaded valve plungers with a purge chamber positioned between the plungers. A high pressure gas supply which contains a gas, either of the same composition as that in the vessel or a neutral gas, is connected to the purge chamber through a pressure regulator and flow sensor. When either of the two plungers remain unseated, purge gas flows from the purge gas supply through the purge chamber and the unseated plunger. The ow of gas through the ow sensor operates an audio signal device.

BACKGROUND OF THE INVENTION In some storage systems leakage into the tank is hazardous or otherwise deleterious to the system. For example, with the use of pressure relief valves in a vessel containing slush hydrogen or other readily oXidizable material, a very dangerous condition would be present if the relief valve did not completely close and air were to leak into the vessel.

SUMMARY OF THE INVENTION According to this invention, a purge gas chamber is provided between two spring-loaded plungers of a relief valve connected to a tank or vessel containing hazardous liquid or gas. A purge gas, which is either a neutral gas or the same gas as in the tank, is supplied to the purge chamber from a purge gas supply. A pressure regulator senses a drop in pressure in the purge chamber and starts the ow of purge gas into the purge chamber. A ow of gas from the purge supply is sensed to provide an audio signal to indicate a malfunction in one of the plungers.

BRIEF DESCRIPTION OF THE DRAWING FIG. l shows a pressure relief valve assembly according to the invention; and

FIG. .2 shows a cap structure for converting the device of FIG. 1 to conventional use.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawing reference number shows a pressure relief valve connected to a storage tank shown schematically at 12. The tank 12 may contain slush hydrogen or other readily oxidizable material such as methane or other fuels.

The relief valve has a body member 13 with a central passage forming a purge chamber 14 positioned between two spring-loaded plungers 16 and 17. A vent port 22 communicates with central passage 23 in cap member 19. The plunger 17 is located in a cap member 19 and separates the cavity in members 13 and 19 into two chambers 14 and 15. An adjustable threaded plug 20 closes chamber and adjusts spring 21. Cap member \19 is threaded to body member 13 at 24 and acts as an adjustment means for spring 25. Springs 21 and 25 are adjusted so that plunger 17 opens at a lower pressure than plunger 16.

Purge gas from supply 28 is supplied to purge chamber ice 14 through a pressure regulator shown generally at 30 and a ow sensor shown generally at 32. A shutol valve shown schematically at 34 may also be provided. The spring 36 of pressure regulator 30 is adjusted to open valve 37 when the pressure on the purge chamber side of valve 30 drops to a predetermined level. A ow of gas through oritice 39 causes diaphragm 41 and arm 42 to move contact 43 into engagement with contact 44 against the action of spring 45 thus energizing signal device 46. A flexible seal 47 is provided around contact arm 42.

A cap member 19 is shown in FIG. 2 and may be used in place of cap member 19 to convert the relief valve to the conventional operation. In this case tube 49 would be removed to provide a vent for the valve.

In the Ioperation of the device when the pressure in tank 12 exceeds the level as determined by spring 25, plunger 16 opens allowing gas to leak into purge chamber 14. Since spring 21 is adjusted to permit operation of plunger 17 at a lower pressure than plunger 16, plunger |17 opens almost immediately to vent gas through port 22. In normal operation, the plungers 16 and 17 close again when the pressure in tank 12 drops below the desired pressure as set by spring 25. If plungers 16 or 17 malfunction and do not close, or if both malfunction and the pressure in purge chamber 14 drops below the level set by spring 36, valve 37 is Opened permitting the ow of purge gas from supply 28 through regulator valve 37, flow sensor 32, and into purge chamber 14 and through the open plunger or plungers. A flow of gas through sensor 32 operates signal device 46, thus giving an alarm that there is a malfunction. The spring 36 is set to open valve 37 at a pressure higher than the pressure in the atmosphere outside port 22 but lower than the pressure required to open plunger 16 as determined by the setting of spring 25. Thus, there will always be a flow out through plunger 17 whenever it is open. If only valve 16 remains open due to malfunction, purge gas will iiow into tank 12 if the tank pressure drops below the pressure as determined by the setting of spring 36.

There is thus provided a pressure relief valve assembly for preventing the hazardous leakage of gas into a storage tank due to a malfunction of the valve plunger.

While a certain specific embodiment has been described, it is obvious that numerous changes may be made without departing from the general principles and scope of the invention.

I claim:

1. A pressure relief valve assembly comprising a body member having a iirst and a second port communicating with a cavity within the body member; spring-operated valve means positioned between said ports for dividing said cavity into a lirst and a second chamber; a second spring-operated valve means for admitting'gas from a storage tank to the first of said chambers when the gas in the tank exceeds a first predetermined pressure; means closing the second chamber for adjusting said first springoperated valve means to a lower opening pressure than said second valve means; means for admitting a purge gas to said irst chamber when the pressure therein drops below a second predetermined level lower than the opening pressure of said irst valve means.

2. The device as recited in claim 1 including means for indicating a ilow of said purge gas.

3. The device as recited in claim 2 wherein said indicating means includes an audio signaling device.

4. A pressure relief valve assembly comprising; a lirst member having a central passage therethrough; a first valve means for closing one end of said passage; a rst spring within said passage abutting said valve means; means, closing the other end of said passage for vadjusting said spring to thereby adjust the opening pressure for said valve means; a passage through the wall of 3 4 said -rst member; a second member having a central 5. The device as recited in claim 4Vncluding means passage therethrough; a second valve means closing one for indicating a ow of gas from said purge gas supply end of the passage in said'second member; a second into said chamber. spring within the passage of said second member and 6. The device as recited in claim 5 wherein said indiabutting said second valve means; said rst member c1oseating means includes an audio signaling device.

ing the other end of the passage of said second member 5 to thereby provide a closed chamber in said second mem- References Clted ber; aidfrst drnertnber lbeing adg'lustable on lid lsaecorld UNITED STATES PATENTS mem er or a Jus lng t e secon spring o ere y a p just the opening pressure for the second valve means; a 10 Calr passage through the Wall of said second member; a 3349793 10 /1967 Bacllh 1'37 3Z2 purge gas supply connected to the passage through the wall of said second member; means connected between HENRY T KLINKSIEK Primal, Examiner the purge gas supply and said second member for ady mitting purge gas to the chamber in said second mem- 15 U S CL X'R ber when the pressure therein drops below a predeter- 73 46. 137 512 mined pressure. 

